In the pre-distortion technology, a digital pre-distorter (DPD) whose property (amplitude and phase) is opposite to that of a transformation function is cascaded before a nonlinear power amplifier (PA), to change in advance an input signal to be opposite to the property of the power amplifier, so that input and output of the PA presents an overall linear relationship. Because the nonlinear property of the power amplifier changes in actual environment due to factors such as temperature, humidity, a supply voltage, component aging, and channel switching, in order to ensure stable linear output of a system, the digital pre-distorter is required to adjust automatically according to a change of the property of the power amplifier.
As shown in FIG. 1, in the prior art, in order to dynamically adjust, by using an algorithm, distortion caused by a nonlinear amplifier PA, some circuit adjustment circuits are added, which are called observing circuits (including a coupler, a down converter, an analog-to-digital converter (ADC), and an algorithm module that are connected in sequence in FIG. 1). In FIG. 1, after obtaining a distorted signal of the PA, the coupler converts the distorted signal to a base band signal by using the down converter; the analog-to-digital converter (ADC) performs analog-to-digital conversion; and the algorithm module performs adjustment by using a specific algorithm, so as to ensure that a signal subsequently input to a DPD is linearly output after being processed by the PA.
As can be known from FIG. 1, in the foregoing solution of the prior art, in order to implement the pre-distortion technology, some circuits (observers) need to be added in an original time division duplexing (TDD) transceiver system, which doubtlessly increases hardware costs of the system.